Study On Load Condition For In-Service Bridges

The term reliability-based bridge design refers to procedures in which specification bodies consider the statistical distributions of loadings and the statistical distribution of component strengths. The reliability is calculated from these load and resistance distributions. Research in the area of bridge design has been and still is concentrated on the study of the strength of materials and relatively few studies have been performed on traffic loads and their effects. Traffic loads have usually been assumed to be given in codes. This is mainly because it is very difficult to model traffic loads in an accurate manner because of their randomness.A complete evaluation of the condition of a bridge requires the knowledge of actual traffic load and how they are distributed to different bridge components.In this work, the traffic load model based on measurements of real traffic loads in Shanghai was used to make bridge reliability assessment and posting analysis. The following outline gives an overview of the general content of this thesis.(1) Traffic load measurementsThe stochastic process of traffic load can be described by filtered composite renewal process, which determines the traffic measurements contain both inter-vehicle distances measurements and vehicle weight measurements. It is easy to achieve the distribution of the collected data by statistical analysis method. (2) Modeling of traffic loadsBy using the M-C simulation, the site-specific traffic load model was established based on measurement of real traffic load.(3) Reliability assessment and posting analysis of real existing bridgesSeven typical type of medium and short span bridge were chosen to made reliability assessment based on extreme value distribution of the traffic load effects. At last, bridges posting analysis were made through modification test of the traffic load models.